In 2015, the International Court of Justice ruled that Bolivia’s claim against Chile could proceed to the merit stage, setting up this Article’s discussion of perhaps the most intractable border dispute in South American history – Bolivia’s attempt to reclaim from Chile a ‘sovereign access to the Pacific Ocean’. This Article investigates the international law and deeply commingled regional history pertaining to the Atacama Desert region, the hyperarid yet resource-rich region through which Bolivia seeks to secure its long-lost access to the sea. Investigating the factual circumstances (effectivités), the post-colonial international legal principle of uti possidetis, territorial temptations arising from resource discoveries, and the duty to negotiate based on a pactum de contrahendo, a pactum de negotiando, or unilateral declarations, this Article concludes this case is less suited for adjudicative settlement than resolution by the principal three parties involved in the region – Bolivia, Chile, and Peru – primarily because the parties have, over the course of this protracted dispute, constructed intersubjective modalities for a shared sovereignty arrangement facilitated by sub-regional economic growth relations. A regional reconstruction of sovereignty in the northern Atacama region presents the better prospect for resolution than is possible through the limited outcomes presented by formal third party dispute settlement.